Mr Pompeo is in Brussels for talks among foreign ministers at NATO, where its European members have been criticised by Mr Trump for failing to spend enough on their own defence and relying too much on Washington.

In a speech to diplomats, Mr Pompeo said Mr Trump was not seeking to be "undermining these institutions, nor is he abandoning American leadership" but was in fact "rallying the noble nations of the world" for an order that "achieves greater prosperity for all."

"Even our European friends sometimes say we're not acting in the world's interest. This is just plain wrong. Our mission is to reassert our sovereignty, reform the liberal international order," he said.

Russia remains defiant

The bloc also imposed economic and other sanctions on Russia since it annexed Ukraine's Crimean Peninsula in 2014, but there is little appetite among the allies to broaden those measures as Russia remains defiant.

Despite NATO launching its biggest military build up in Europe since the Cold War, Russia's actions near the Sea of Azov demonstrate that the increased allied presence won't deter its aims in eastern Ukraine.

Of similar concern to NATO is Russia's new SSC8 missile system.

The US has shared intelligence evidence with its allies that the ground-fired cruise missile could give Moscow the ability to launch a nuclear strike in Europe with little or no notice.

Washington says the system contravenes the 1987 Intermediate-range Nuclear Forces Treaty, which bans all land-based cruise missiles with a range between 500 and 5,500 kilometers, and President Donald Trump is threatening to pull out of the bilateral pact.

"It's urgent that Russia ensures full compliance in a transparent and verifiable way, because the INF treaty is so important for our security," Mr Stoltenberg told reporters Tuesday.

Some European allies suspect that Mr Trump could give notice in coming months that the US is leaving the treaty.

That would give Russia a notice period of six months to decide whether to comply.